Combination plastic watch case and crystal



June 4, I968 Y J, SHJFFMAN 3,386,239

COMBINATION PLASTIC WATCH CASE] AND CRYSTAL Filed June 16, 1966 INVENTOR. MW e5 ATTORNEY;

United States Patent 3,386,239 COMBINATION PLASTIC WATCH CASE AND CRYSTAL Jerome Shilfman, 128 Cartage Road, Scarsdale, N.Y. 10583 Filed June 16, 1966, Ser. No. 558,069 3 Claims. (CI. 58-91) ABSTRACT OF THE DISCLOSURE A plastic watch case and crystal, the crystal having an external thread configuration that mates with an internal thread configuration of the watch case and bears upon the bezel to seal the case against moisture.

The present invention relates to combined watch cases and crystals and has for its object to provide a combination in which the watch movement is placed in the case from the top thereof and the crystal is employed to bear upon the bezel, preferably through the placement of an intermediate gasket washer and by rotation or partial rotation of the crystal, the crystal being rotated in, holding the watch movement against relative motion in the assembly, and sealing the case against the entrance of moisture or contamination.

Heretofore certain watch cases have been made of plastic, but with a circular channel cut into the plastic case above an annular shoulder. In such case it has been necessary to cut the circular channel by a tool applied to the inner peripheral wall after the molding of the plastic watch case. Thus the molded watch cases had first to be removed from the molds and cooled, then removed to a cutting machine with a rotary cuttin tool for forming the circular channel, and then cleansed from the inevitable powdered plastic particles from the cutting operation. Thus the universal practice has been to produce an annular groove, and then to force the crystal into the groove.

A further disadvantage in such universal practice as stated above is found in the repair of watches. In assembling the crystal with the plastic watch case, the crystal is buldged by forces directed inwardly from the outwardly flared periphery of the crystal, as by a tool specially designed for such purpose, and the crystal is snapped into the channel and expands outwardly. It is diflicult to remove the crystal for watch repair and reinsertion, without such damage to the crystal that it is frequently discarded when the watch movement has to be repaired.

By means of the present invention, the aforesaid difficulties are removed, by my discovery that the periphery of a crystal may be formed with an overlying flange and a shallow straight skirt provided with projecting elements, and that the inner face of the watch case may be formed with an upper flange, the latter receiving the overlying flange of the crystal, and said inner face of the watch case being formed on its inner wall with projecting elements which interlock with the coating elements of the crystal, when the latter is placed in a given position on the watch case, is depressed, and is rotated until the assembly is tight.

The accompanying drawings are, with the exception of FIG. I, greatly enlarged.

In the drawings, which show embodiments of the invention:

FIG. 1 is a perspective view showing an assembled watch case and crystal as an embodiment of the invention, looking toward the top of the crystal;

FIG. 2 is an enlarged longitudinal section taken on the line 22, FIG. I;

3,386,239 Patented June 4, 1968 FIG. 3 is a composite view showing a second form of the invention, with the watch case inclined forwardly and the crystal in reverse inclination;

FIG. 4 is a composite view similar to FIG. 3 showing a third embodiment of the invention;

FIG. 5 is a view similar to FIGURES 3 and 4 showing an additional form within the invention.

Referring to FIGURES 1 and 2 of the drawing, it will be seen that the annular body 1, carrying spaced arms 2 at opposite sides, is internally formed with a lowermost shoulder at 3 and an uppermost shoulder at 4. Intermediate the said shoulders, the inner wall of the case body 1 is formed with continuous female thread 5 to receive a coacting thread on the skirt of the crystal 6.

Intermediate the flange 6 of the crystal and the uppermost flange of the watch case body 1, there is preferably placed a resilient clear washer, as illustrated in said FIG. 2, at 7.

In molding the watch case body 1, which will generally be by injection molding, the core of the mold may be removed by rotation thereof. Equally well, the crystal, when it is molded, may be removed from the field of the mold, by rotation. In the molding of the watch case body 1, its base, opposite the crystal, may be closed by an integral wall, forming an element of the body, or a flanged metallic plate, such as that shown at 8, may be placed in the mold to receive the plastic forming body 1 and hence become a fixed part thereof.

The crystal should be molded from a clear plastic having hardness and strength, one example being Lucite, well known as an acrylic resin. For the watch case body, I have found that the plastic should be of very durable properties in that it will have tough and rigid characteristics, yet non-brittle, together with a high-melting factor, with resistance to shock and deformation under stress. One such plastic composition is Delrin (Du Pont de Nemours Company), of which the general purpose composition Delrin 500 is satisfactory.

Returning to the drawings, it will be seen that the same numeral references as employed in FIGURES l and 2 are used in FIGURES 2 to 5 inclusive, the differences over FIGURE 2 being in the formation of the crystal skirt, and the inner wall formation of the watch case body 1, and also in that the uppermost flange of the watch case body is broken at one or more points.

On FIG. 3 the skirt of the crystal, below flange 6, is formed with a single outwardly projecting thread indicated at 9, and the flange 4 of the watch case body 1 is provided with a corresponding thread-receiving channel at 10. In said construction, flange 4 is provided with a gap 11 leading to the top end of the thread-receiving channel 10.

In FIG. 4, the crystal is assembled with the watch case body by normal clockwise rotation. The skirt of the crystal is formed with a plurality of thread-projections 12, in this case four engaged to be received in recessed threads 14 formed in the inner wall of the watch case body 1, and the flange 4 of the latter is provided with a gap at the receiving end of each recessed thread 14.

In FIG. 5' a bayonet-lock formation is employed for the assembly. To that end the crystal 6 is formed with a plurality of wedge projections on its skirt below flange 6 as shown at 15. The watch case body 1 has its flange 4 provided with a gap for reception of each wedge 15, the gap leading to a channel having an inclined lower face coasting with the Wedge projection 15 of the crystal, in each case, to securely hold the crystal, and yet permit rotation of the latter for its removal by a friction device applied to the top of the crystal.

In each case the crystal may be firmly applied to the watch case body by slight downward pressure and frictional rotation. Removal of the crystal from the watch case body can readily be made by reverse action upon the crystal. In the meantime, the watch movement is held and protected against shock whilst removable upon disassembly of crystal from the case body. Also it will be noted that the skirt of the crystal, strengthened as it is by the circumferentially arranged rib formations thereon, supplies added protection to the movement and to the strength of the assembly as a whole.

Referring to FIG. 2, member 3 thereof, in some cases the latter member may be a crystal and secured to the watch case body in the same manner as crystal 6, so that the watch movement may be inserted from the bottom of the case. Thus both surfaces of the watch movement will be visible. It also will be noted that the position of the elements 6 and 3 of FIG. 2 may be reversed with element 8 being a crystal.

It will be understood that various modifications may be made in the elements and their arrangement from those illustrated in the drawings, without departing from the spirit of the invention. Thus the reversal of the skirtcarried projections and watch case body formed channels, as to their positions, is within the spirit of the invention.

Having described my invention, what I claim and desire to secure by Letters Patent is as follows:

1. In combination, a plastic watch case body having a normally round inner opening for the crystal and leading to a cavity for the reception of a watch movement, at least one inclined channel in the inner face of said watch case body and leading from an entrance gap at an end of said channel, and a transparent crystal having a top area and having an annular depending skirt merging with said top area, said skirt being integrally formed with at least one inclined-faced, annularly positioned, projection externally thereof, said projection being adapted to enter said channel of the watch case body at said gap thereof, said crystal being rotatable on the watch case body to slide said projection into said channel and thereby move the crystal toward the base of the watch case body.

2. A combined watch case body and crystal constructed in accordance with claim 1, in which the crystal is formed with a plurality of spaced wedge-shaped projections on and externally of the skirt, the Watch case body being formed with an annular rim and shoulder means below said rim, said shoulder means being formed with a plurality of gaps, each gap leading to a wedge-shaped opening in said shoulder means, for reception of the wedge-shaped projections of the crystal.

3. A combined watch case body and crystal constructed in accordance with claim 1, in which the watch case body is normally open at both face and bottoms thereof, and means at both face and bottoms of the watch case adapting the crystal to be inserted and held, thereby making both faces of the watch movement visible.

References Cited FOREIGN PATENTS 177,165 1/ 1923 Great Britain. 155,519 6/1932 Switzerland. 304,785 1/ 1955 Switzerland.

RICHARD B. WILKINSON, Primary Examiner.

G. H. MILLER, 1a., Assistant Examiner. 

